Vehicle occupant seated weight detection systems are useful in connection with air bags and other pyrotechnically deployed restraints as a means of characterizing the occupant and determining if airbag deployment should be disabled. In particular, the seated weight of the occupant may be used to distinguish between large and small occupants, and between a small occupant and an empty seat. For example, a large occupant is deemed to be present if the measured seated weight (MEAS_WT) is above an “allow” threshold (THR_ALLOW) corresponding to a minimum large occupant seated weight such as 60 lbs; a small occupant is deemed to be present if MEAS_WT is between THR_ALLOW and an “occupied” threshold (THR_OCC) corresponding to a minimum small occupant seated weight such as 12 lbs; and the seat is deemed to be empty if MEAS_WT is less than THR_OCC. Typically, airbag deployment is suppressed in the case of an empty seat or a small occupant, and not suppressed in the case of a large occupant, although in some cases reduced force deployment is allowed for a small occupant.
In most systems, the status of airbag suppression is visually conveyed to the occupants by means of an instrument panel lamp, referred to herein as a Passenger Airbag Disabled (PAD) lamp. A typical requirement is that the PAD lamp should be unlit when the seat is empty, lit when the seat is occupied by a small occupant, and unlit when the seat is occupied by a large occupant, as depicted by the table of FIG. 1. Of course, various other strategies are also possible; for example, the PAD lamp can have a separate state for indicating that the seat is empty, reduced force deployment can be enabled for a small occupant as mentioned above, and so on. In any event, the measured weight of an occupant (or an inanimate object for that matter) tends to vary somewhat due to occupant weight shifting and vehicle movement, resulting in oscillation of the suppression status, particularly if MEAS_WT is close to THR_OCC or THR_ALLOW. Such oscillation is undesired of course, and the accompanying oscillation or toggling of the PAD lamp tends to annoy the occupants and undermine their confidence in the suppression system. While hysteresis can be employed to prevent repeated changes in the occupant status due to minor oscillation of the measured weight, experience has shown that hysteresis alone is inadequate. Accordingly, what is needed is a more robust method of determining and indicating the suppression status of a weight-based airbag suppression system.